When the political activist Al Sharpton pivoted from his war against bigmouth radio man Don Imus to a war on bad-mouth gangsta rap, the instinct among older music fans was to roll their eyes and yawn. Ten years ago, another activist, C. Delores Tucker, launched a very similar campaign to clean up rap music. She focused on Time Warner (parent of TIME), whose subsidiary Interscope was home to hard-core rappers Snoop Dogg and Tupac Shakur. In 1995 Tucker succeeded in forcing Time Warner to dump Interscope.

Her victory was Pyrrhic. Interscope flourished, launching artists like 50 Cent and Eminem and distributing...